1. Field of the Invention
The present invention relates generally to a magnetic head and magnetic head apparatus, and more particularly, to a magnetic head and magnetic head apparatus for recording and reproducing information to and from a flexible rotating recording medium in a state in which the magnetic head floats over the flexible rotating recording medium due to an air flow generated between the magnetic head and the flexible rotating recording medium.
2. Description of the Related Art
Generally, an ordinary magnetic disk drive that uses a flexible magnetic disk having a coercive force of 900 oersted (Oe) or less as a magnetic recording medium allows a relatively low rotational speed of for example 300 rpm to 720 rpm. In this case, magnetic recording and reproduction is performed by causing the magnetic head to be in direct sliding contact with the magnetic disk.
However, with recent advances in high-density recording on magnetic disks, the rotation speed of the magnetic disk has been increased to for example 3000 rpm, with the coercive force of the magnetic disk being increased to 1500 Oe or more. As a result, in order to accommodate such so-called high-capacity magnetic disks a magnetic disk drive has appeared in which the magnetic head is provided with a narrow gap. Hereinafter such a magnetic disk drive will be referred to as a high-capacity magnetic disk drive.
Since a high-capacity magnetic disk drive allows the magnetic disk to be rotated at high speeds, the magnetic disk and the magnetic head used therein may be easily damaged if the magnetic head were to be caused to be in direct contact with the magnetic disk, as is done in the conventional magnetic disk drive.
As a result, the high-capacity magnetic disk drive is designed so that the magnetic head floats in an elevated state over the surface of the high-capacity magnetic disk due to an elevating force arising as a result of an air flow caused by a relative speed between a slider surface of the magnetic head and the magnetic disk. Magnetic recording and reproduction is performed while a state of non-contact between the magnetic head and the magnetic disk is maintained.
FIGS. 1, 2, 3, 4 and 5 show a magnetic head used in the conventional high-capacity magnetic disk drive.
As shown in FIGS. 1 and 2, the conventional high-capacity magnetic head 1 generally comprises a slider 2 and a magnetic head unit 3. The slider 2 supports the magnetic head unit 3 and causes the magnetic head unit 3 to float over the magnetic disk 6, as shown for example in FIG. 3.
The top surface of the slider 2 forms an air bearing surface for forming an air bearing with respect to the magnetic disk 6. Additionally, a central groove 2a is formed at a central position of the top surface of the slider 2. As shown in FIG. 1, the central groove 2a divides the air bearing surface into a first air bearing surface 2b located to the right side of the central groove 2a and a second air bearing surface 5 located to the left side.
The magnetic head unit 3 and a pair of grooves or slots 4 are provided on the first air bearing surface 2b. The magnetic head unit 3 for performing magnetic recording and reproducing is formed by sandwiching a gap member between thin plates of magnetic cores.
The slots 4 extend in a tangential direction of the magnetic disk 6, that is, in the direction of arrow X in FIG. 1, and provide a vent for an air flow produced between the magnetic disk 6 and the first air bearing surface 2b. By providing a vent to the air flow produced between the magnetic disk 6 and the first air bearing surface 2b, an elevating force exerted on the magnetic head 1 is reduced. Accordingly, by providing the slots 4, the elevating force of the magnetic head 1 can be controlled.
As described above, the second air bearing surface 5 is formed to the left of the central groove 2a located on the top surface of the slider 2 as shown in FIG. 2. Like the first air bearing surface 2b, the second air bearing surface 5 also produces a force for elevating the magnetic head 1.
FIG. 3 is a lateral cross-sectional view of a conventional magnetic head as seen from a direction of disk approach thereto. As shown in the drawing, a pair of magnetic heads 1 are supported so as to be opposite each other within the magnetic disk drive. The elevating force generated by the second air bearing surface 5 described above exerts a force that pushes the magnetic disk 6 in the direction of the first air bearing surface 2b, that is, in the direction of the magnetic head unit 3, of the opposite magnetic head 1. Accordingly, the second air bearing surface 5 also functions as a pressure pad for pressing the magnetic disk 6 toward the opposite magnetic head 1.
Additionally, as described above, slots 4 are formed in the first air bearing surface 2b. The slots 4 provide a vent for the air flow produced between the magnetic disk 6 and the first air bearing surface 2b, thus reducing the elevating force exerted on the magnetic head 1. Accordingly, the magnetic disk 6 is deformed by a negative pressure generated in the slots 4 and a pressure generated at the second air bearing surface 5 due to a change in air flow so as to warp toward a gap 31 as the magnetic disk 6 rotates between the pair of magnetic heads 1. With this construction, optimum recording and reproduction of information to and from the magnetic disk 6 is ensured even with floating magnetic heads 1.
FIG. 6 is an oblique view of a second example of a conventional magnetic head, in which the magnetic head is provided with both a high-density R/W gap and a lowdensity R/W gap. The magnetic head la comprises a slider, a first magnetic head unit 3a and a second magnetic head unit 3b. 
A central groove 2a is formed at a central position of the top surface of the slider 2. As shown in FIG. 6, the central groove 2a divides the top surface of the slider into two surfaces. A first air bearing surface 9a is located in the figure to the left side of the central groove 2a, with the high-density R/W gap being formed on the first air bearing surface 9a. A second air bearing surface 9b is formed parallel to the first air bearing surface 9a on a side of the central groove 2a opposite the side on which the first air bearing surface 9a is formed, with the low-density R/W gap being formed on the second air bearing surface 9b. A pair of grooves or slots 4 is formed so as to extend the length of the first air bearing surface 9a. 
The magnetic head 1a having the structure described above can be adapted to a 300 rpm low-density mode or a 3600 rpm high-density mode, depending on the type of recording medium.
A description will now be given of how the magnetic head 1 faces the magnetic disk 6, with reference to FIG. 4 and FIG. 5 FIGS. 4 and 5 show views of a state in which the magnetic head 1 is recording information to or reproducing information from a magnetic disk 6, from a radial direction Y of the magnetic disk 6.
FIG. 4 shows the magnetic disk 6 in a state of optimal approach to the magnetic head 1.
As shown in FIG. 4, a pair of slots 4 are formed in the first air bearing surface 2b in which the first magnetic head unit 3 is provided. These slots 4 are formed along the entire length of the first air bearing surface, that is, from a leading edge 7 of the magnetic head 1, that is, an edge side of the magnetic head 1 at which the magnetic disk 6 enters the magnetic head 1, to a trailing edge 8 of the magnetic head 1, that is, an edge side of the magnetic head 1 at which the magnetic disk 6 exits the magnetic head 1. As a result, a reduction in the elevating force due to the presence of the slots 4 is generated over the entire extent of the length of the first air bearing surface 2b. 
Accordingly, even in a state of optimal approach a distance H between the magnetic disk 6 and the leading edge 7 of the magnetic head 1 in the above-described construction in which the slots 4 are provided is smaller than a corresponding distance in a construction in which the slots 4 are not provided.
Moreover, with such a construction the magnetic disk 6 is maintained in close proximity to the magnetic head unit 3 as a result of the reduction in elevating force by the slots 4, thus providing optimal magnetic recording and reproduction.
By contrast, FIG. 5 shows a state in which the magnetic disk 6 approaches the magnetic head 1 at a height position lower than that of an optimal approach. Such a small-clearance state of approach results from the flexibility of the magnetic disk 6 or from inevitable errors in the production process thereof. This phenomenon is called penetration.
When the height of the magnetic disk 6 upon approach to the magnetic head 1 is lower than a standard optimum height position as described above, the distance H is reduced to such an extent that the magnetic disk 6 may come into contact with the leading edge 7 of the magnetic head 1, and the magnetic disk 6 or the leading edge 7 of the magnetic head 1 may be damaged as a result.
Additionally, if a structure is used in which no slots 4 are provided in an effort to prevent damage to the magnetic disk 6 due to this penetration, the magnetic disk 6 and the magnetic head unit 3 become separated and it becomes impossible to obtain optimal magnetic recording and reproduction.
Accordingly, it is a general object of the present invention to provide an improved and useful magnetic head in which the disadvantages described above are eliminated.
The above-described object of the present invention is achieved by a magnetic head comprising:
a first magnetic head unit for recording and reproducing information to and from a first flexible rotating recording medium;
a second magnetic head unit for recording and reproducing information to and from a second flexible rotating recording medium having a coercive force lower than a coercive force of the first flexible rotating recording medium; and
a slider supporting the first and second magnetic head units, the slider having a central groove separating a first air bearing surface at which the first magnetic head unit is provided and a second air bearing surface at which the second magnetic head unit is provided, the slider generating an elevating force from an air flow generated in a space between the first and second air bearing surfaces and the flexible rotating recording media,
the first air bearing surface having a width on a leading edge side thereof perpendicular to a direction of approach of the flexible rotating recording medium and a width on a trailing edge side thereof disposed opposite the leading edge side, the width of the leading edge side being greater than the width of the trailing edge side.
Additionally, the above-described object of the present invention is also achieved by magnetic head as claimed in claim 1, wherein the width of the first air bearing surface in a direction perpendicular to a direction of approach and retreat of the flexible rotating recording medium gradually declines from the leading edge toward the trailing edge.
According to the invention described above, a sufficient elevating force due to the generation of air flow between the slider and the recording medium can be maintained at the leading edge and a hard collision between the recording medium and the slider at the leading edge can thus be prevented. In addition, because the elevating force gradually decreases toward the trailing edge the recording medium can be brought into close proximity to the magnetic head for optimal magnetic recording and reproduction.
Additionally, the above-described object of the present invention is also achieved by the magnetic head as described above, wherein:
a periphery of a flat surface forming the first air bearing surface is chamfered; and
the leading edge of the first air bearing surface has a width equal to a distance to a first interference wave appearing at both lateral edges of the first air bearing surface as measured using an optical flat placed on the first air bearing surface.
According to the invention described above, the dimensions of the flat surface forming the first air bearing surface remain unchanged even if the shape of the chamfered edge changes, so a constant elevating force can be maintained.
Additionally, the above-described object of the present invention is also achieved by the magnetic head as described above, wherein:
the first air bearing surface is divided into a first surface part and a second surface part by a lateral incision extending in a direction perpendicular to the direction of approach of the flexible rotating recording medium; and
a width of the second air bearing surface in a direction perpendicular to the direction of approach of the flexible rotating recording medium is either constant or gradually declines from a leading edge side of the second air bearing surface toward a trailing edge side of the second air bearing surface.
According to the invention described above, the elevating force at the first air bearing surface can be adjusted and the distance between the first magnetic head and the disk for optimal magnetic recording and reproduction. In addition, the elevating force at the leading edge of the second air bearing surface can be maintained at an appropriate level, so a hard collision between the disk and the slider can be prevented and damage to the disk avoided.
Additionally, the above-described object of the present invention is also achieved by the magnetic head as described above, wherein the lateral incision has a depth greater than a depth of the central groove.
According to the invention described above, the weight of the magnetic head is reduced, thereby improving tracking.
Additionally, the above-described object of the present invention is also achieved by the magnetic head as described above, wherein a pivot is provided between the first and second magnetic head units at a point of flotation of the magnetic head units.
Additionally, the above-described object of the present invention is also achieved by the magnetic head as described above, wherein a distance N between the pivot and a hypothetical line extending from a leading edge side of the second surface part of the first air bearing surface in a direction perpendicular to the direction of approach of the flexible rotating recording medium is not more than 2 mm.
According to the invention described above, wherein the point of flotation is the point at which a combined elevating force acts on the magnetic head, the elevating force is adjusted appropriately and collision between the recording medium and the slider can be avoided. In addition, a constant elevating force can be maintained and the magnetic head can be elevated effectively for optimal magnetic recording and reproduction.
Additionally, the above-described object of the present invention is also achieved by the magnetic head as described above, wherein the leading edges and the trailing edges of the first and second air bearing surfaces are curved so as to be slanted with respect to the flexible rotating recording medium.
Additionally, the above-described object of the present invention is also achieved by the magnetic head as described above, wherein the angle of slant of the leading edges and the trailing edges of the first and second air bearing surfaces with respect to the direction of approach of the flexible rotating recording medium is not less than 2xc2x0 and not more than 45xc2x0.
Additionally, the above-described object of the present invention is also achieved by the magnetic head as described above, wherein a width of the curved portions of the leading edges and trailing edges of the first and second air bearing surfaces in a direction perpendicular to the direction of approach of the flexible rotating recording medium is not less than 0.05 mm and not more than 0.5 mm.
According to the invention described above, by curving the edges of the air bearing surfaces so as to be slanted with respect to the disk within an angle of slant that does not affect the elevating force, contact between the disk and the magnetic head can be prevented or, in the event of such contact, damage to the disk can be reduced.
Additionally, the above-described objects of the present invention are also achieved by the magnetic head as described above, wherein:
a first interference line appearing by placing an optical flat on at least one of either the first air bearing surface or the second air bearing surface and measuring the interference lines is rounded with a radius R of not less than 0.2 mm and not more than 1.0 mm at comer portions on the leading edge side of at least one of the periphery of the flat surface forming the first air bearing surface and the periphery of the flat surface forming the second air bearing surface; and
the first interference line is rounded with a radius of not less then 0.2 mm and not more than 1.0 mm at corners of edges of the first surface part and corners of edges of the second surface part disposed opposite each other across the lateral incision.
According to the invention described above, any contact between the magnetic head and the disk is a line and not a point, and so a force of contact between the magnetic head and the disk can be dispersed and damage to the disk can be avoided.
Additionally, the above-described objects of the present invention are also achieved by a magnetic head apparatus adapting the magnetic head as described above, wherein:
the magnetic head units are disposed opposite each other;
a read/write gap provided on the second magnetic head unit is positioned closer to the leading edge of the magnetic head than a read/write gap provided on the first magnetic head unit; and
an eraser gap provided on the second magnetic head unit is positioned closer to the leading edge side of the magnetic head than a core of the first magnetic head unit.
According to the invention described above, the distribution of weight of the magnetic head is well balanced center and optimal magnetic recording and reproduction can be obtained from the second magnetic head unit in particular.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.